Electrical system for use in photorecording



Feb. 18, 1947.

N. A. HASSLER ELECTRICAL SYSTEM FOR USE IN PHOTORECORDING Filed July 3l, 1944 Patented Feb. 18, 1947 ELECTRICAL SYSTEM FOR USE IN PHOTORECORDIN G Norman A. Hassler, Duncan, Okla., assignor to Halliburton Duncan, Okla.

Oil Well Cementing Company,

Application July 31, 1944, Serial No. 547,486

6 Claims.

This invention relates to electrical systems for use in photorecording and more particularly to an arrangement in which a photosensitive recording surface such as a film is moved with respect to an electrical incandescent lamp and subjected to the light emitted by the lamp.

In photorecording systems it is frequently den sirable to move a photosensitive recording surface such as a film at varying speeds. For example, in the electrical logging of oil wells a photosensitive iilm is geared to an electrode which is lowered into the oil well and a correlation is made between the depth of the electrode in the Well and a particular point on the nlm. The movement of the electrode in the well cannot be maintained at a uniform speed, and so the lm in the recorder cannot be moved at a uniform speed.

The sensitivity of film to light bein'g uniform, a record made by subjecting the film to a source of light is not good if the intensity of the light remains constant while the lm is moved at diierent speeds. To remedy this defect mechanical means have heretofore been proposed. For example, the size of the aperture through which the light shines upon the lm has been reduced when the speed of the film is reduced from standard so as to compensate for the change in speed.

It is an object of the present invention to devise electrical means for controlling or regulating the amount of light emitted by an electrical incandescent lamp to cause it to be in direct proportion to the speed of a moving object, such, for example, as the speed of a film.

It is a further object of the invention to provide means for exposing a photographic nlm to light uniformly while moving the film at varying speeds, by regulating the amount of light projected upon the lm and causing the amount of light to be in proportion to the speed of the film moving past the light.

Other objects and advantages reside in certain novel features of the arrangement, as will be apparent from the following description taken in connection with the accompanying drawing, in which:

The single figure is a diagrammatic representation of an electrical system illustrating one way of carrying out the principles of the present invention.

Referring to the drawing in detail, it will be seen that a photographic film is shown at It, mounted for movement with respect to an electrical incandescent lamp I I which causes a beam of the light I2 to pass through an aperture I3 to project a spot of light I4 upon the lm I0. 'Ihe spot of light I4 causes a line I4' of uniform exposure to appear on the lm when the film is developed. The mechanism for moving the iilm Ill is not shown in the drawing, and forms no part of the present invention, but mechanism in diagrammatically shown which is responsive to movement of the film Il). This is shown merely as a roller I5` on a shaft I6, which is geared to the film, with a disk I1 mounted on the shaft I6 (although in actual practice a gear train may be employed to make the relative angular speeds of the disk I1 and the roller I5 other than unity).

The disk I1 contains a number of uniformly spaced perforations or holes I8. This deviceis known as a chopper and serves to interrupt the passage of light from an incandescent lamp I9 to a photoelectric cell 20. A beam of light from the lamp I9 passing through one of the holes I8 to the cell 20 is illustrated in the drawing by the dash line 2I. Since this beam of light passes through the holes I8, the speed of rotation of the disk I1 controls the frequency of the interruptions of the light beam 2l.

One element of the photoelectric cell 20 is grounded as shown at 22. The other is connected by means of wire 23 to resistance coupling associated with the input circuit of a vacuum tube T1 which functions as an alternating current amplifier. The resistance coupling is illustrated as consisting of a condenser 24, a resistance 25 connected to the positive terminal of a B battery 26, and a resistance 29. The condenser 24 is connected to the grid 21 of the vacuum tube T1 and a small battery 28 connected to the resistance 29 puts a negative bias on the grid 21.

The cathode 3B of the tube T1 is grounded as illustrated. Throughout the drawing the tubes are illustrated as having indirectly heated cathodes. To simplify the diagram, the "A supply to the filaments are not included.

The plate 3l of tube T1 is connected through resistance coupling to the grid 3-2 of the tube T2. The resistance coupling is the same as that for the tube T1, and consists of a condenser 33, a resistance 34 connected to the positive terminal of a B battery 35 and a resistance 31. A small battery 35 is connected to resistance 31 to put a negative bias on the grid 32. The cathode 38 of the tube T2 is grounded and the plate 39 is resistance coupled to the control grid 40 of the tube T3. As before, the resistance coupling between the tubes T2 and Ts includes a condenser 4I and a resistance 42 connected tothe positive terminal of a B battery 43 and a resistance 45.

A small battery Eli is connected to resistance 45 to put a negative bias on the grid dil.

The tube Ta contains an auxiliary grid lila which is connected to the cathode 55, both the grid 40a and the 'cathode (i6 being connected through a resistance 4l, and a condenser [i3 to the plate 49 of the tube T3. A B battery Eil connected directly thereto supplies the potential to the plate 49.

The tube T1 functions as an ordinary alternating current amplifier. The current in the output of this tube has a frequency the same as that of the interruptions of the beam of light 2| by the perforated disk Il. Thus the tube T1 together Withthe chopper Il, cell and connections constitutes an alternating current generator, the frequency of which is proportional to the speed of the film I.

The tube T2 also functions as an alternating current amplier and the frequency of its out-n put is the same as that of the tube T1. However, this tube is overloaded and the output thereof has a wave shape which is approximately square.

The tube Ts is a gas-filled tube and the output therefrom is unidirectional, there being a pulse in the plate circuit each time the disk il permits the flow of light from the lamp I9 to the cell 2D.

The square wave output of tube T2 is applied to the grid of tube T3 in such a manner that the grid receives a voltage pulse of short duration once each cycle which serves to start conduction in the plate circuit of tube Ts. When tube T3 is conducting, condenser 48 discharges through it and the current limiting resistance fil. When condenser 48 is discharged, tube T3 ceases to conduct until the next cycle and condenser 43 recharges. This charging current flows through the milliammeter 53 and its associated circuit. Thus the metering circuit current consists of a series of unidirectional pulses of equal energy value Whose average current, as read by the milliammeter 53, depends only upon the frequency lwith which they occur. This frequency is proportional to the rate of rotation of the perforated disk il, and proportional to the speed of film Hl. If desired, this milliammeter may be calibrated in units of speed.

To eliminate the effect of pulsations of current in the system an electrical filter may be connected across the resistance 52 and the milliammeter 53, this filter being illustrated in the drawing as consisting of a condenser 5S. The adjustable resistance in parallel with resistance 52 and mlliammeter 53 serves as a calibration control and may be used to compensate for variations between tubes should it be necessary to change them.

The apparatus so far described might be termed an electrical speedometer or electrical frequency meter in which the frequency is controlled by the speed of a moving object, in this case the film lil. Since the lm Il) may be geared to some other object such as an electrode being moved in an oil well, or since the disk Il' may be geared to some other object moving in synchronism therewith it is obvious that the electrical system could be used to measure the speed of devices other than that illustrated in the drawing.

From what has been shown above, it will now be clear that if the lamp Il is caused to emit light in proportion to the amount of energy in the plate circuit of the vacuum tube T3, it will also nit light in proportion to the speed of the lm An adjustable tap 51 is provided on the resistance 52 so that the voltage drop across the portion of the resistance 52 between the tap 51 and the ground is taken off. This tap 5l is connected through a number of resistances to the grid 58 of a tube T4, by means of a wire 59. The resistances in series are designated SQ, 6i and 52.

In the circuit illustrated, potential on the grid 58 depends upon voltage drops across these resistances. A battery 63 in series with a Variable resistance 54 is connected across resistance 6l and a battery 65 in series with a photoelectric cell @5 is connected across the resistance 62, which is variable. An A. C. source 6l in seriesl with a variable resistance 63 is connected across resistance tt. With such a circuit, there is a voltage drop across each of the resistances 52, Si), El and `E2. The algebraic sum of the D, C. voltage drops across resistances 52, Si and t2 due to the output of the tube T3 and to the batteries 63 and 55 respectively constitutes the D. C. potential or regulating bias on the grid 5&3 and may be said to modulate the A. C. voltage drop across resistance due to the source 6l, all of these voltagel drops being impressed upon the grid 58.

The plate l0 of tube T4 is connected by resistance coupling to the grid H of tube T5, the resistance coupling consisting of the condenser 72, resistance 'I3 connected to the positive terminal of B battery 74 and resistance 16. To place a bias on the grid 'l l, a small battery 'i5 has its negative terminal connected to the grid 'H through the resistance i6.

The output of the tube Ts is similarly connected to an amplier tube Te, the plate 'I9 of the tube T5 being connected through a condenser 89 to the grid li. A B battery 82 has its positive terminal connected through a resistance El to the plate Til and a small battery A83 has its negative terminal connected through resistance dll to the grid il. rThe plate 85 of the tube Te is connected to the primary Sl of a transformer which is in turn connected to the positive terminal of a B battery 88. A condenser 89 is connectedacross the primary ci. The secondary 9G of the transformer is connected to the filament of the lamp l i.

The amplification of an A. C. voltage by a triode is a function of the D. C. potential or bias on its grid. The D. C. Voltage drop across resistance iZ due to output of tube T3 is one component of the bias on the grid 58 of tube T4. Therefore, variations in voltage of the ouput 0I" tube Ta affect the A. C. output of tube T4, and consequently the energy supplied to the lamp l l. The output of tube T3 must be so connected, as to polarity, that an increase in voltage drop across resistance 52 causes an increase in output of tube T4.

By means of the variable resistance 64, the voltage drop due to the battery 53 is adjusted to introduce an additional bias voltage into the circuit of grid 58 which serves to adjust the light output of lamp I l to zero when the voltage drop across resistance 52 is zero.

By means of the variable resistance 63, the A. C. voltage from the source 67 across resistance '5t should be made of such magnitude that the lamp H will have the maximum desired light output when the grid bias of tube T4 is such that its amplification is a maximum. The frequency of source 57 should be high enough that the amplifier may be designed to amplify it without also amplifying the Variations in voltage across resistance 52. For example, the frequency of source @i may be 1,500 cycles per second where the maximum rate of change in the voltage drop across resistance 52, is less than that of a corresponding A. C. voltage of several cycles per second.

By means of variable resistance 62 an adjustment can be made when lamp I I is giving off light, which will vary the amount of light given off by the lamp I I to bring about a predetermined relation between the light output and a given voltage drop across resistance 52. As shown hereinafter, this relation, when once obtained for a given voltage drop across resistance 52 is automatically maintained by the circuit which includes the cell 66, without further adjustment.

The photoelectric cell 66 referred to above is placed adjacent the incandescent lamp II so as to be illuminated by a beam of Vlight therefrom. In the drawing this is indicated by the dash line 8| passing through an aperture 92.

During operation, there are only two factors which vary or control the amount of energy supplied to the lamp II through the amplifier network, these being the amount of direct current voltage variation across resistance 52 and the variation in voltage across resistance 62 caused by the variation in the current flow through the photoelectric cell 65 (the resistances 64 and E8 not being adjusted during operation and the voltages of the sources 6l, 63 and 65 remaining constant).

In the absence of the circuit containing the photoelectric cell E5, the amplifier network shown is such as to cause an alternating current to be applied to the lamp II, the voltage of which is approximately proportional to the direct current voltage drop across resistance 52. If the lamp I I emitted light in proportion to the voltage applied thereto, no further control would be necessary to accomplish the purpose of the invention, but there are no known incandescent filament lamps which have this characteristic.

To cause the lamp II to approach the desired operation, that is, to cause it to emit more or less light in proportion to increase or decrease in the voltage drop across resistance 52 and hence in proportion to the speed of film ii), the system of the present invention has been devised.

The photoelectric cell 66 and the associated battery 65 and resistance 62 may be said to constitute a photoelectric negative feed-back circuit from the lamp I I to the tube T4. This feed-back circuit causes the change in the amount of light given off to become proportional to the voltage drop across resistance 52.

This function is accomplished in part by the selection of values for the component parts of the photoelectric cell circuit so that the voltage across the resistance B2 will be proportional to the intensity of the light striking the cell from the lamp II. Since the current flow of the cell 66 varies in proportion to the light intensity therein, the voltage drop across the resistance 62 varies in proportion to the intensity of the light given off by the lamp I I.

In addition to the selection of proper values, the arrangement must be such that the voltage across resistance t2 is introduced into the grid circuit of tube T4 in opposition to the voltage drop across resistance 52. The diiference between these voltages then controls the amount of energy supplied to the lamp I I. If this difference is made small, i. e., if the voltage drop across the resistance E2 is made approximately equal to the voltage drop across resistance 52 then the light output will be approximately proportional to the voltage drop across resistance 52. The voltage drop across the resistance 62 cannot be made absolutely identical with the voltage drop across resistance 52 because if that condition always prevailed there would be no change in input to the tube T4. However, the amplifying network can be so designed as to have high amplification, so that the difference in these voltages required to obtain any desired lig.-t output from the lamp II will be very small.

It will be apparent that the system is not dependent upon the exact relation of current to light intensity of the lamp II or to any other characteristics of the lamp II. The photoelectric feed-back circuit is such that the characteristics of the lamp are not controlling of the amount of energy fed back. The amount of light emitted is the controlling factor.

Since there are a number of photoelectric cells on the market, and since some have been designed to be sensitive to particular light waves, care should be exercised in selecting the cell. The photoelectric cell 66 should be so selected as to be sensitive to the same range of the spectrum as that to which the film it is sensitive, if the best results are to be obtained with that film.

In the accompanying drawing only one eme bodiment of the invention is shown and the circuits involved here have been reduced to the simplest possible forni in which they will operate and illustrate the principles involved. This was accomplished by making each voltage supply separate and independent of all others. It is to be understood that in practice all D. C. voltages necessary for the operation of the various circuits may be derived from a common power supply. The required circuit changes, stabilizing networks and decoupling networks necessary to permit this are known to those skilled in the art and need not be described here.

Thus, it is obvious that various changes may be made without departing from the spirit of the invention or the scope of the annexed claims.

I claim:

l. An electrical control system comprising a thermionic amplifier network, a lamp connected to the output thereof and an arrangement for causing said lamp to emit light in proportion to the speed of a moving object, said arrangement including means driven in synchronism with the moving object for generating an alternating current the frequency of which is proportional to the speed of the moving object, means for impressing a regulating bias on said amplifier network proportional to the frequency of the alternating current so generated and photoelectric means for modifying the regulating bias in accordance with the'intensity of the light given off by said lamp.

2. An electrical control system comprising an alternating current thermionic amplifier network, a lamp connected to the output thereof and an arrangement for causing said lamp to emit light in proportion to the speed of a moving object, said arrangement including means driven in synchronism with the moving object for generating an alternating current the frequency of which is proportional to the speed of the moving object, means for generating a direct current the voltage of which is proportional to the frequency of the alternating current so generated, means for impressing a regulating bias on said amplifier network proportional to the voltage of the direct current so generated and photoelectric means for modifying the regulating bias in accordance with the intensity of the light given off by said lamp.

3. An electrical control system comprising a thermionic amplifier network, a lamp connected to the output thereof and an arrangement for causing said lamp to emit light in vproportion to the speed of a moving object, said arrangement including means driven in synchronisrn with said object for generating a direct current the voltage of which is proportional to the speed of the moving object, means for impressing a regulating bias on said amplier network proportional to the voltage of the direct current so generated and photoelectric means for modifying the regulating bias in accordance with the intensity of the light given oi by said lamp.

4. An electrical system adapted for use in combination with photosensitive material exposed to light emitted from a source of light while moving the material past the source at varying speeds, said system including a thermionic amplifier network, a lamp connected to the output thereof and adapted to provide the source of light for exposing the photosensitive material and an arrangement for causing said light to emit light in proportion to the speed of the material past the lamp, said arrangement including means driven in synchronism with the material for generating a source of current, some characteristic of which is proportional to the speed of the material, means for impressing a regulating bias on said amplifier network in proportion to variations in such characteristic and photoelectric means for modifying the regulating bias in accordance 8 With the intensity of the light given oi by said lamp. 1

5. An electrical system adapted for use in combination with photosensitive material exposed to light emitted from a source of light while moving the material past the source at varying speeds, said system including a thermionicamplier network, a lamp connected to the output thereof and adapted to provide the source of light for exposing the photosensitive material and an arrangement for causing said light to emit light in proportion to the speed of the material past the lamp, said arrangement including means for impressing a regulating bias on said amplifier network in proportion to the speed of said photosensitive material and photoelectric means for modifying the regulating bias in accordance with the .intensity of the light given off by said lamp.

6. An electrical control system comprising a thermionic amplifier network, a lamp connected to the output thereof and an arrangement for causing said lamp to emit light in proportion to the speed of a moving object, said arrangement including means for impressing a regulating bias on said amplifier network in proportion to the speed of the moving object and photoelectric means for modifying the regulating bias in accordance with the intensity of the light given off by said lamp.

NORMAN A. HASSLER. 

